ABSTRACT
A challenge for chemical ecologists is to understand the ecological functions of complex essential oils (EOs) produced by plants. Sensitive analytical methods, genetic manipulation/plant breeding, and sophisticated physiological/behavioral bioassays have facilitated progress toward this goal. Aromatic plants from Mediterranean environments are important natural sources of essential oils. Multidisciplinary studies revealed fine-scale geographic polymorphism in foliar EOs from Thymus vulgaris in southern France. Single monoterpenoids dominate these “chemotypes,” whose adaptive value depends on soil type, local climate, herbivore pressure, and competition with neighboring plants. Similar habitats in Greece feature aromatic shrubs (Cistus creticus, Lavandula stoechas) that serve as hubs in plant-pollinator networks dominated by native bees. The putative connection between sesquiterpene EOs and non-volatile resins, collected from these plants by bees as propolis, is reminiscent of well-documented resin collection in tropical habitats, from specialized Dalechampia and Clusia flowers as well as wounded trees, to be used as nesting materials by female stingless bees and orchid bees. In the same habitats, male orchid bees collect EOs from hundreds of orchid species along with Anthurium species in the Araceae family, providing specialized pollination services. The chapter closes with a survey of rewarding and deceptive pollination modes driven by EO chemistry in the aroid family.
